from datetime import datetime

from sqlalchemy import Column, DateTime, ForeignKey, Integer, String, UniqueConstraint
from app.database import Base


class UserCollection(Base):
    __tablename__ = "user_collections"

    id = Column(Integer, primary_key=True, index=True)
    user_id = Column(Integer, ForeignKey("users.id", ondelete="CASCADE"), nullable=False)
    title = Column(String(200), nullable=False)
    created_at = Column(DateTime, default=datetime.utcnow)
    # When it was last opened or added to. Null means never since this was
    # recorded, which is not the same claim as "never used".
    last_used_at = Column(DateTime, nullable=True)


class UserCollectionQuestion(Base):
    __tablename__ = "user_collection_questions"
    __table_args__ = (UniqueConstraint("collection_id", "question_id", name="uq_collection_question"),)

    id = Column(Integer, primary_key=True, index=True)
    collection_id = Column(Integer, ForeignKey("user_collections.id", ondelete="CASCADE"), nullable=False)
    question_id = Column(Integer, ForeignKey("questions.id", ondelete="CASCADE"), nullable=False)


class UserCollectionArticle(Base):
    """An article put aside into a library.

    Its own table rather than a nullable `article_id` beside `question_id` on
    the row above: that shape allows a row with both, or with neither, and
    every read then has to say which kind it is looking at. Two tables, one
    unique constraint each, and a library is the union of them.
    """

    __tablename__ = "user_collection_articles"
    __table_args__ = (UniqueConstraint("collection_id", "article_id", name="uq_collection_article"),)

    id = Column(Integer, primary_key=True, index=True)
    collection_id = Column(Integer, ForeignKey("user_collections.id", ondelete="CASCADE"), nullable=False)
    article_id = Column(Integer, ForeignKey("articles.id", ondelete="CASCADE"), nullable=False)